dual Vista boot with c: drive letter

I would like to have two bootables copies of vista (this gives to me the
possibility to make tests on the second partition without touching the first
one).
First of all I've installed the system on c: partition with everything I
need (and it's a long work).
At this point, with XP, I made a copy of the partition with Partition Magic
and, modifying the boot.ini,
I obtained two bootable OS that was alternatively renamed c: by the boot
manager.
I've tried to copy the Vista partition with Acronis, then I've managed the
BCD with Easy BCD but when I start on the second partition I've all system
variables pointing to d: but the desktop and the programs still points to
the first partition.
With the suggestions of R. C. White I've understood that, installing a
second vista copy from within the first one, creates exactly what I want
(two bootable versions of vista that are renamed c: at boot).
So the trick is possible.
What I cannot reach is to make a copy (or a restore from a wim file) in a
second partition and modify the bcd to get c: letters on the two vista
copies.
Can someone help me in this?

Might it not be easier and more effective as a testing OS to install a copy
of Vista as a virtual OS?
Something malicious installed on either copy of bootable Vista could still
take down your entire computer.

> Might it not be easier and more effective as a testing OS to install a
> copy of Vista as a virtual OS?

This is a better idea than mine to obtain an "experimental" machine.
In this days, I've studied VmWare and VMX Builder, discovering the possible
uses of virtual machines.
I've always thought to VmWare as a way to install different OS, but I was
wrong.
Thanks a lot, although I've not solved the problem, I've find a better way
of working.